1. Field of the Invention
The present invention relates to a filter for an in-tank type fuel pump to be used in a vehicle.
2. Description of the Prior Art
A prior art will be described with reference to FIGS. 8 and 9. FIG. 8(a) is a side elevational view of a filter, and FIG. 8(b) is a sectional view thereof. FIG. 9 is a side elevational view of a pump assembly including the filter disposed in a fuel tank.
As seen in FIG. 9, the pump assembly includes a bracket 102 mounted on a fuel tank 101 so as to close an upper opening thereof and carrying a pump supporting stay 103, a fuel feeding pipe 104, a return pipe 105 and a connector 106 for electrical connection.
An electrically operated fuel pump (also referred to as a fuel pump) 108 is an integral combination of an electric motor such as a brushless motor or a D.C. motor and a pump section driven by the motor, and is supported in a slant manner by the pump supporting stay 103.
The fuel pump 108 has in the upper surface thereof a discharge port (not shown) to which is connected the fuel feeding pipe 104 through a connecting hose 109, and is provided on the upper surface thereof with a terminal 110 to which a harness 106a of the connector 106 is electrically connected. Furthermore, the fuel pump 108 has on the bottom surface thereof a suction port (not shown) to which is attached a filter 112 which will be mentioned later.
The pump assembly thus constructed is disposed in the fuel tank 101 in the following manner. Specifically, the fuel pump 108 and other components are inserted into the fuel tank 101 through the opening in the upper surface to be immersed in fuel in the tank, and the bracket 102 is fixed so as to close the opening. Though not illustrated, a pipe for feeding fuel to an engine is connected to the fuel feeding pipe 104, and another pipe for returning excess fuel from the engine to the tank is connected to the return pipe 105. A harness to be coupled to an electric circuit including a power source is connected to the connector 106.
The fuel pump 108 thus disposed in the fuel tank 101 is operated to suck fuel in the fuel tank 101 through the filter which is supplied through the fuel feeding pipe 104 to the engine.
Now, the description will be related to the filter 112 assembled to the pump assembly with reference to FIGS. 8 and 9.
The filter 112 includes a frame 113 to be mounted on the fuel pump 108, a bag type screen 114 to be kept in an expanded condition by the frame 113, and a flat protector 115 to be interposed between the screen 114 and a bottom surface 101a of the fuel tank 101.
The frame 113 is made of a synthetic resin material such as a nylon resin, and composed of an inner skeleton 117 inserted in the screen 114, a cylindrical connecting pipe 118 integrally formed with an end of the skeleton 117 and an elbow type mounting pipe 119 to which the connecting pipe 118 is attached through snap fitting or the like. The inner skeleton 117 is provided with a band type main plate 121, holding pieces 122 projecting vertically from the upper and lower surfaces of the main plate at regular intervals, a presser portion 123 provided at the extreme end of the main plate 121 and projecting from the lower surface thereof, and a thin portion 124 formed in the main plate 121 in the vicinity of the connecting pipe 118. The mounting pipe 119 is formed with a fixing piece 125 to be clipped onto a pump body of the fuel pump 108.
The screen 114 is made of a synthetic resin material such as a nylon resin in the form of a mesh suitable to filter fuel and has good flexibility. The screen 114 is formed into a bag by inserting the central portion of a fold edge of the screen 114 which is folded in half in the mounting pipe 119, securing the connecting pipe 118 of the inner skeleton 117 to the mounting pipe 119, and welding the peripheral edges of the screen together.
The protector 115 is a substantially rectangular thin plate made of a synthetic resin material such as a nylon resin. The protector 115 is provided at an end thereof with a mounting piece 126 to be mounted on the mounting pipe 119 of the frame 113.
The filter 112 is mounted on the fuel pump 108 by fitting the mounting pipe 119 to the suction port of the fuel pump 108 and clipping the fixing piece 125 onto the pump body, as shown in FIG. 9. It should be noted that the filter 112 prior to installation in the fuel tank 101 extends substantially at right angles with respect to the fuel pump 108 as shown by phantom lines in FIG. 9.
On installation of the pump assembly in the fuel tank 101, the filter 112 is forcedly bent as shown by solid lines in FIG. 9. At this time, as the frame 113 is bent at the thin portion 124, both the screen 114 and the protector 115 are also bent. This causes the lower surface of the screen 114 to be pressed against the tank bottom surface 101a with the protector 115 interposed therebetween. The protector 115 is provided for elimination or reduction of abrasion of the lower surface of the screen 114.
In such a prior art filter 112, the mounting piece 126 of the protector 115 is used to mount the protector 115 on the mounting pipe 119 of the frame 113.
Thus, when disposed in the fuel tank 101, the protector 115 is deformed by bending. This results in a strong force applied by the protector 115 against the tank bottom surface 101a, and consequently, vibration generated through operation of the fuel pump 108 is apt to be transmitted through the protector 115 to the fuel tank 101, causing increased vibrational noise. The force by which the whole filter presses the bottom surface 101a of the fuel tank 101 is equal to the sum of the bending forces of the frame 113, of the screen 114 and of the protector 115.
Prior to installation, the protector 115 is apt to open or to extend apart from the screen 114 as shown by phantom lines in FIG. 8(b), causing reduction in the efficiency of operation with regard to assembling of the fuel pump 108, insertion of the fuel pump 108 into the fuel tank 101 and others operations.
Furthermore, the prior art filter 112 has an upper mesh portion and a lower mesh portion adhered to each other along a line 116 which is at a level substantially corresponding to a half of the full height of the filter 112, resulting in little allowance of the membrane length of the lower mesh portion 114b left.
Thus, when the filter 112 is bent to be installed in the fuel tank 101, vibration may cause the holding pieces 122 of the inner skeleton 117 of the frame 113 to stretch the lower mesh portion 114b, with the inner skeleton 117 supported by the lower mesh portion 114b. This will disturb bending of the inner skeleton 117 and often cause engagement of the central portion of the bent inner skeleton 117 against the protector 115, with the presser portion 123 floating above the protector 115.
Such engagement of the central portion of the inner skeleton 117 against the protector 115 decreases the distance from the engagement point to the filter bending point, resulting in increase of the force applied by the filter 112 against the tank bottom surface 101a. Thus, vibration generated by operation of the fuel pump 108 will be more readily transmitted to the fuel tank 101, causing increased noise.